The Influence of Ionic Liquids on the Nanostructure of Polyimide based Aerogels

Aerogels are promising materials for many aerospace applications, including high performance antennae and flexible insulation because of their inherent low density-high surface area properties. Polymeric aerogels, more specifically polyimide aerogels (PIA), provide excellent mechanical properties beyond traditional silica aerogels while maintaining the required thermal stability. NASA has investigated PIA paired with ionic liquids to develop novel mechanically robust electrolyte systems for next generation batteries. PIA surface area, porosity, and pore volume are important properties; however, these measurements are traditionally conducted sans solvent. Because of this, the impact of the ionic liquid on the nanoscale structure of PIA is unclear. To determine the impact of solvent presence, we use small angle neutron scattering to determine solvated PIA skeletal size and composition. Our results indicate that the pores as well as the polyimide skeleton absorb solvent. The amount of solvent uptake in the struts is dependent upon ionic liquid structure as well as polyimide structure. These results broaden the characterization of polymeric aerogels and provide the ability to correlate structural characteristics to their performance.